1. Field of the Invention
The present invention relates to a supporting apparatus for an optical scanning apparatus which may be utilized in a laser printer, a digital copying machine, a laser facsimile machine, etc., and more particularly to a supporting apparatus for plural optical scanning apparatus.
2. Discussion of the Background
One of a conventional optical scanning apparatus includes an optical housing in which a laser source, a deflector having a polygon mirror, and a focusing system are installed. In the optical scanning apparatus, a laser beam emitted from the laser optical source is deflected by the polygon mirror and is focused on, for example, a scanning surface of a photoconductive element by a focus lens of the focusing system. Such an optical housing for an optical scanning apparatus includes a mounting reference surface for a polygon motor which is one element of a deflecting device and for an optical system. The polygon mirror and the optical system are often mounted on the reference surface in a vertical direction. Further, there is a conventional image forming apparatus which is composed of plural optical scanning apparatus, such as a color image forming apparatus. In the color image forming apparatus, the plural optical housings are installed as a frame structure.
In order to compensate for an inclination error in a sub-scanning direction, a relation between the scanning surface and each optical scanning apparatus needs to be adjusted accurately. However an adjustment work is difficult because of a rigidity of the optical housing, the frame, etc., and because an adjustment structure is large. Especially, when the plural optical scanning apparatus are installed and plural image forming stations are required in order to form the color image, the adjustment structure is much larger.
Therefore, as described in Japanese Laid Open Patent Nos. 4-131872 or 4-131876, it is proposed that an error of an image with respect to a reference image forming station is compensated for by a method that an angle of a mirror for returning a laser beam is changed by actuators. However, as plural actuators are needed in order to change the mirror in the apparatus, the structure is complicated and the assembly time increases.